Simultaneous determination of tartaric acid and potassium in wines using a multicommuted flow system with dialysis

Abstract

A multicommuted flow system with the propulsion device placed before detection is proposed for the determination of tartaric acid and free potassium in table and Port wines. A dialysis unit was introduced to increase sample dilution and minimize matrix interferences. The determination of tartaric acid was based on the spectrophotometric monitorization of the complex formed by the dialyzed analyte with vanadate. Potentiometric measurement of potassium was carried out through an ion selective tubular electrode. Dynamic linear ranges of 0.500-5.00gL(-1) and 390-2000mgL(-1) were achieved for tartaric acid and potassium determinations, respectively. Detection and quantification limits of 0.1 and 0.4gL(-1) of tartaric acid were obtained, respectively. For the potentiometric determination, a detection limit of 1x10(-4)molL(-1) was achieved. The accuracy of the method was assessed by analysis of 30 wine samples by the proposed methodology and manual procedures. There were no statistical differences between the 2 sets of results, in both determinations. Relative standard deviations lower than 2.1 and 2.4% were attained by the spectrophotometric and potentiometric measurements, respectively. A determination rate of 52h(-1) was achieved.

Membrane-based Separation in Flow Analysis for Environmental and Food Applications

“…Similar to GDU, dialysis is also used in food analysis for matrix removal and sample dilution to fit high concentrations in the linear range of calibration curve therefore increasing the precision of the method. In the works by Silva, Álvares-Ribeiro, Oliveira et al (67,85) a dialysis unit was introduced in the flow system to attain sample dilution and minimize matrix interferences in wine analysis. Donnan dialysis has been scarcely used in combination with flow techniques in spite of providing high enrichment factors for cations probably due to the requirement of an ionic strength gradient.…”

Various instrumental approaches for determination of organic acids in wines

“…The widely employed analytical methods for determination of organic acids in wine are focused on the total quantity of acids in wine. To date, capillary electrophoresis (CE) with direct and indirect detection (Golubenko, Nikonorov, Nikitina, 2012;Gomez, Monasterio, Vargas, Silva, 2012), high performance liquid chromatography in various modes (Flores, Hellin, Fenoll, 2012;Lin, Liu, Shen, Yang, 2011), enzymatic flow injection analysis (Oliviera, Lopes, Toth, Rangel, 2010) and titrimetic techniques were performed. As a very interesting alternative, the gas chromatography with mass spectrometry detection without any derivatization step was used (Jurado-Sanchez, Ballesteros, Gallego, 2011).…”

Influência de etapas do processo de vinificação na acidez de vinhos elaborados com uvas Vitis labrusca

“…Entre os fatores que interferem no equilíbrio ácido-base e que modificam o pH estão a dissolução dos minerais e ácidos orgânicos da película e da polpa da uva durante o contato da casca com o mosto; a síntese de ácidos orgânicos durante a fermentação alcoólica; a degradação do ácido málico em ácido láctico durante a fermentação maloláctica; e a precipitação do ácido tartárico na forma de bitartarato de potássio e tartarato neutro de cálcio (RIBÉREAU-GAYON et al, 2006;OLIVEIRA et al, 2010).…”

“…Segundo Rizzon, Miele e Meneguzzo (2000), a variedade Isabel, que, assim como a Terci, é um cultivar da espécie Vitis labrusca apresenta características que não favorecem o aumento de pH na vinificação devido ao tamanho da baga, relação película/polpa e teor de potássio do mosto. Outro fator que pode modificar o pH dos vinhos, além da fermentação maloláctica, é a precipitação do ácido tartárico na forma de bitartarato de potássio e tartarato neutro de cálcio (OLIVEIRA et al, 2010). Entretanto, neste caso a diminuição da acidez parece não estar associada a este fator, uma vez que não foi observada correlação em nível de significância satisfatório entre as concentrações de potássio e de ácido tartárico em relação à acidez.…”